I stumbled on Eliza Durling Cook in the 1860 US Census for Clinton, Iowa living with her husband, Jackson Cook, her sons, William (11 yrs.), Thaddeus (9 yrs.), James (7 yrs.), and Frank (2 yrs.).Also living in her home was Luther Durling (28 yrs.) who is one of Garret and Catherine Durling's sons.This leads me to believe Eliza was one of Garret's children as well.She fits the age of one of his daughters (unnamed) in the 1840 census in New York.Eliza is also in the 1870 US Census (Lyons Ward 6, Clinton, Iowa)listed as the head of the house.Her husband may have passed away.Hope this helps!